Discontinuous distribution of N-oxidation of dietary-derived trimethylamine in a British population

Abstract

1. Whilst the majority of individuals within a British white population are able to convert > 90% of their dietary-derived trimethylamine to its N-oxide, outliers exist who show varying degrees of decreased metabolism. Such individuals, excrete unoxidized trimethylamine in their urine and, if N-oxidation is sufficiently low, may experience malodour problems (Fish-Odour Syndrome).

2. Such observations have now been extended to a much larger group (n = 421; 221 males) of British white volunteers recruited from staff and students of Imperial College Medical School at St Mary's, London. Each subject collected a 0–24-h urine sample, which was subsequently analysed for total trimethylamine and trimethylamine N-oxide content.

3. Sixteen subjects (3·8% population; seven male, nine female) excreted <90% of their total trimethylamine output as N-oxide. All six subjects who excreted <80% as N-oxide (indicative of potential heterozygous status for deficient N-oxidation—fish odour syndrome) were female.